Update Cargo.lock to allow compiling with wgpu backend (#160)

This PR builds upon #159 and updates a few dependencies in `Cargo.lock`
so that `eframe_template` can be compiled with the `wgpu` backend
*without* removing and regenerating `Cargo.lock` from scratch.

Before this change, the following compile error occurs after switching
from `glow` to `wgpu` backend:

```
ben@Bens-MacBook-Pro eframe_template % cargo check
error: failed to select a version for `termcolor`.
    ... required by package `naga v0.20.0`
    ... which satisfies dependency `naga = "^0.20.0"` of package `wgpu v0.20.1`
    ... which satisfies dependency `wgpu = "^0.20.0"` of package `eframe v0.28.0`
    ... which satisfies dependency `eframe = "^0.28"` (locked to 0.28.0) of package `eframe_template v0.1.0 (/Users/ben/Documents/Fractals/eframe_template)`
versions that meet the requirements `^1.4.1` are: 1.4.1

all possible versions conflict with previously selected packages.

  previously selected package `termcolor v1.4.0`
    ... which satisfies dependency `termcolor = "^1.1.1"` (locked to 1.4.0) of package `env_logger v0.10.1`
    ... which satisfies dependency `env_logger = "^0.10"` (locked to 0.10.1) of package `eframe_template v0.1.0 (/Users/ben/Documents/Fractals/eframe_template)`

failed to select a version for `termcolor` which could resolve this conflict
```

So I removed the `termcolor` entry from `Cargo.lock` and recompiled so
that it would choose another version that works:

```
ben@Bens-MacBook-Pro eframe_template % cargo check
error: failed to select a version for `js-sys`.
    ... required by package `wgpu v0.20.1`
    ... which satisfies dependency `wgpu = "^0.20.0"` of package `eframe v0.28.0`
    ... which satisfies dependency `eframe = "^0.28"` (locked to 0.28.0) of package `eframe_template v0.1.0 (/Users/ben/Documents/Fractals/eframe_template)`
versions that meet the requirements `^0.3.69` are: 0.3.70, 0.3.69

all possible versions conflict with previously selected packages.

  previously selected package `js-sys v0.3.66`
    ... which satisfies dependency `js-sys = "^0.3"` (locked to 0.3.66) of package `eframe v0.28.0`
    ... which satisfies dependency `eframe = "^0.28"` (locked to 0.28.0) of package `eframe_template v0.1.0 (/Users/ben/Documents/Fractals/eframe_template)`

failed to select a version for `js-sys` which could resolve this conflict
```

Then I did the same for `js-sys` and recompiled:

```
ben@Bens-MacBook-Pro eframe_template % cargo check
error: failed to select a version for `wasm-bindgen-futures`.
    ... required by package `wgpu v0.20.1`
    ... which satisfies dependency `wgpu = "^0.20.0"` of package `eframe v0.28.0`
    ... which satisfies dependency `eframe = "^0.28"` (locked to 0.28.0) of package `eframe_template v0.1.0 (/Users/ben/Documents/Fractals/eframe_template)`
versions that meet the requirements `^0.4.42` are: 0.4.43, 0.4.42

all possible versions conflict with previously selected packages.

  previously selected package `wasm-bindgen-futures v0.4.39`
    ... which satisfies dependency `wasm-bindgen-futures = "^0.4"` (locked to 0.4.39) of package `eframe_template v0.1.0 (/Users/ben/Documents/Fractals/eframe_template)`

failed to select a version for `wasm-bindgen-futures` which could resolve this conflict
```

And finally I did the same for `wasm-bindgen-futures` and recompiled,
and it worked just fine.

I'm not sure if this is the proper way to resolve this issue. Let me
know if I should have done something different.